Nothing To Do And All Day To Do It In
What we are on about is the business of setting your camera to do its own thing and then tootling off to leave it to the job. Time delay for one shot is available on nearly all cameras - you select the delay and press the go button and then scurry around to be in the thing. I do it all the time in the studio - not just for selfies, but to allow a camera time to settle onto a tripod and yield steady results. Nothing new here.
Interval shooting is another thing altogether. We have all seen wonderful animations of flowers opening, clouds scudding across a sky, or investors besieging a ponzi financier's office. These are done by allowing the camera to take successive shots at spaced intervals. In the case of the flowers it can be quite a long interval between shots - the bank panic can be shot with small spacing between the exposures. Believe me, there will be motion...
Some cameras are equipped with interval timers themselves that can do this - I believe my Nikon D300 and 300s can do it. Other cameras can receive an electric signal from a separate timer that will trigger the shutter as long as there is battery power and memory available.
The time frame for this can be staggering - one timer I have in hand right now says that you can extend the recording time to 99 hours, 59 minutes, and 59 seconds. With enough battery power for the camera - a separate issue - you get days of action in one sequence. This can be replayed on computers in the form of a video.
I've also been informed by a customer that there are other time-sequence machines upon which the camera may be mounted that will move the whole rig around during that interval - giving a view of many things happening all round the setup. I can't quite see that this would be controllable but it must be so.
One of our former staff members mentioned that he had been involved in a project at a building site setting up an automatic camera to record the month's-long process of erecting a structure. Apparently the limiting factor was the power supply to the camera.